Subscript indices must either be real positive integers or logicals.

Hi everyone, I'm learning Matlab for university. I need your help to understand how to solve this problem. This is my script:

fc=4;
dt=1/fc;
t=0:dt:19-dt;
s=[ones(1,4*fc) zeros(1,6*fc)];
h=sin(2*pi*t2/15 + pi/4);
figure
plot([0:length(s)-1]*dt,s);
figure
plot(t2,h);
l1=length(s);
l2=length(h);
l=l1+l2-1;
S=fft(s,l);
H=fft(h,l);
conv=ifft(S.*H);
figure
plot(conv,'r-');
y=conv(h,s);
figure
plot(y,'b');

the program gives me the error "Subscript indices must either be real positive integers or logicals" in the line "y=conv(h,s)"...but I don't understand why...I'm going mad, please help me!

[Matt J]

In future, please highlight your code and apply the

formatting button, as I have just done for you now.

[Giovanni]

thank you =)

Answer 1

[Roger Stafford]

You have used the term 'conv' two ways, first as an array and second as the convolution function. In the second usage, matlab still thinks it is now an array, so the h and s are misinterpreted as indices. That is probably the source of your error message.

Lesson to be learned: you should never use the name of a matlab function as also the name of something else. It is "sacrosanct".

[Giovanni]

thank you =) but there is still a problem :S I changed the name of my variable and Matlab still continue with the same error :(

[Giovanni]

no no no ok my mistake =) i cleared all variables and retried and now it goes well =) thank you very much!! =)

Answer 2

[per isakson]

Learn how to use the debugger. It's good!

[Giovanni]

unfortunatly I don't have all this time because my exam is in a few days..

[Matt J]

It takes no more than an hour to learn. You will waste more time if you don't, since you won't have the know-how to cope with future bugs.